Container with tear open seal



Jan. 9, 1968 A. KUHNE 3,362,571

CONTAINER WITH TEAR OPEN SEAL Filed Aug. 2, 1966 ATTORNEYS United States Patent C 3,362,571 CONTAINER WITH TEAR OPEN SEAL Alois Kuhne, Zurich, Switzerland, assignor to Swiss Aluminium Ltd., Chippis, Switzerland, a jointstock company of Switzerland Filed Aug. 2, 1966, Ser. No. 569,627 Claims priority, application lwitzerland, Aug. 9, 1965, 11,158/ 65 7 Claims. (Cl. 220-49) Packages of a tearopen thread which, when pulled, cuts the wall of the package and thereby facilitates opening are well known, as for instance a cardboard box wherein the thread cuts a label separating the lid from the box. This system is also applied to metallic containers where a wire, laid into the connecting fold of the lid, serves as the tear-open means.

The above means are not applicable to the much used plastic or aluminum containers, the lids of which are welded or heat sealed to the container body.

The present invention has to do with such a container comprising a cup-like body having at its upper rim an outwardly bent sealing flange, and a lid the border flange of which is welded or heat-sealed to the sealing flange by means of a plastic material. The containers are manufactured from plastic material, e.g. polyethylene, or from aluminum foil, the latter being known as hard foil containers, and which may have a thickness of up to 0.18 mm. Both body and lid are coated with a layer of, for instance, polyethylene which under pressure and heat causes the sealing of the sealing flange to the border flange. Tear-open threads for such containers have not been used previously, since they cannot be laid within the welded or heat-sealed closure and since such a thread simply laid on the sealing flange within the welded or heat sealed seam does not serve the purpose. The thread has to be fixed to the container in a manner which will enable it to cut the lid along the predetermined line and not to be simply torn out when pulled. In the case of an arrangement Where the lid is folded on the body, the tearopen wire can be placed within the fold of the closure. The present invention now gives the possibility of providing containers with a flange-to-flange seal with a serviceable tear-open seal and tear-open thread.

According to the invention a tear-open thread is applied to the wall of the depressed central portion of the lid extending inside the container body exteriorly of the former wall, and facing the wall of the container body, the ends of this thread coming to the exterior of the container between the sealing flange of the body and the border flange of the lid. The tearing of the thread effects the cutting of a neat and defined line along the edge between the border flange of the lid and the wall of the depressed portion of the lid. The thread is also fixed by the depression of the lid and does not deviate on tearing. Advantageously, the depression of the lid extends over the entire opening of the container body.

The tear-open thread of such a container has to meet rather severe requirements, especially in the case of hard foil containers. It has to resist elevated temperatures, the sealing of the container being performed at about 230 C. The breaking strength is of importance as sheet material of 100 mg and more has to be cut. Moreover this type of container is often sterilized, and swelling of the thread in hot water must be avoided. Furthermore the leading of the thread out from between the flanges has to be considered: it must be suificiently tight.

According to a further development of the invention especially suitable for hard foil containers which have to be sterilized, the tear-open thread is made from twisted single threads of synthetic material which are either spun or extruded.

It has been found that twisted cotton threads as used with cardboard containers do not serve the purpose as they are damaged by the necessary heat sealing temperatures, swell during sterilization and have insufficient breaking strength. One single whole extruded thread or wire made from a material with sufficient resistivity to elevated temperatures and to water during sterilization, viz. from synthetic material, is also unsuitable as it is flattened between the flanges when heat sealed, loses its breaking strength or cannot be pressed tightly into the sealing seam. On the other hand, a twisted thread from synthetic material does not lose its breaking strength even when flattened and can be pressed into the sealing seam without impairing its tightness, the single threads being lain adjacent to each other and are therefore undamaged.

Threads from synthetic polyester materials known under the registered names of Terylene, Trevira, Dacron etc. are especially suitable for the purpose.

The drawing shows as examples two embodiments of the invention:

FIG. 1 is a cross-sectional view of a container with tear open thread;

FIG. 2 is a top plan view of the same container; and

FIG. 3 is a fragmentary cross-sectional view showing a modified form of construction of the portion shown at A in FIG. 1.

A cup-shaped container body 1 manufactured by deepdrawing in the usual manner has at its upper rim portion a sealing flange 2. While the container is shown in the drawing with circular ground-plan, it may be of oval, angular, or of any other shape.

A lid 3 of corresponding shape has a border flange 4 which is welded or heat-sealed to the sealing flange 2 by pressure and heat. The container body and lid may be made from synthetic material, e.g. polyethylene, or from aluminum foil, or the body may be made from one and the lid from another material. The invention is especially advantageous for containers, the body and lid of which are made from aluminum foil. In this case body and lid are heat-sealed in a well known manner by means of an intermediate layer of synthetic material. It is preferable to coat the container body and lid with polyethylene. When sealed by means of a heat-sealing device, the sealing and border flanges are pressed together, the coating melting within the reach of the sealing flange and resulting in a strong and tight seal.

The lid 3 has a depression 10 extending over the entire opening of the container body 1. Against a substantially vertical wall of this depression, facing the wall of the container body, the tear open thread 5 is placed.

It is beneficial to have the wall of the depression slightly inclined inwardly towards the center of the lid, see FIG. 3. Thereby the thread gets a better hold and is less liable to slip downward.

The depression of the lid serves advantageously to keepthe container body dustproof, as the lid can be readily reset after being opened. For this purpose the rim of the container body has a corresponding ridge 6 as shown in FIG. 1.

In FIG. 3 the depression 10 is shaped with an additional bend 7 protruding above the border flange 4. When the container is opened the line of cutting follows this bend thus permitting an easier grip to remove the lid.

The two ends of the tear-open thread 5 are led out between the sealing flange 2 0f the body and the border flange 4 of the lid. The sealing flange 2 is curved inwards at its edge as shown at 8, which serves merely to avoid a sharp edge of the flange and injuries caused thereby, but

has nothing to do with the sealing of the container. At the spot where the thread is led out of the container the inwardly curved portion is cut out. The thread is applied after the curving in of the flange 2 and the ends are fixed by two points protruding into the cut-out part of the curve which are, after application of the thread, pressed together.

At the one end of the thread there is a globule, a seal, or a pull tab 9 facilitating a better grip of the thread. After tearing open, the lid may be entirely removed if the ends of the thread are led out at the same place, or, it may remain connected to the container body if the ends of the thread are led out apart as shown in FIG. 2. It is also possible to unite the two ends of the thread in the same pull tab.

The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the articles hereinafter described and the scope of the application of which will be indicated in the claims.

What is claimed is:

1. A container with a tear-open seal comprising a cupshaped container body with an outwardly-bent sealing flange at its open end, a lid with a depressed central portion and with a border flange sealed to the sealing flange by means of an intermediate layer of material, and a tearopen thread applied exteriorly of said depressed central portion, the lid extending into the open end of the container body, and the ends of thread being led to the exterior of the container between the border flange of the lid and the sealing flange of the container body.

2. A container according to claim 1 wherein the tearopen thread is twisted from single threads made from synthetic material.

3. A container according to claim 1 wherein the depressed portion of the lid is formed at its periphery with a bend protruding to a level above that of the border flange.

4. A container according to claim 1 wherein the depressed portion of the lid is formed with a substantially vertical wall.

5. A container according to claim 4 wherein said substantially vertical wall is inclined inwardly towards the center of the lid.

6. A container according to claim 4 wherein the container body has a side wall with a ridge at its upper rim which recedes inwardly and corresponds to the wall of the depressed portion of the lid.

7. A contained according to claim 1 wherein a gripping means is provided on one of the ends of the tear-open thread led to the exterior of the container.

References Cited UNITED STATES PATENTS 3/1956 Bogner 220-49 9/1959 Vanhoof 229-51 

